Contact filtration of lubricating oils



United States Patent 2,795,535 CONTACT FILTRATION OF LUBRICATING OILSGifford W. Crosby, River Forest, Le Roy W. Holm, Crystal Lake, Robert W.Morrison, Northfield, and Walter J. Sandner, Carpentersville, Ill.,assignors to 'She Pure Oil Company, Chicago, 11]., a corporation of bioNo Drawing. Application December 30, 1952, Serial No. 328,798

7 Claims. (Cl. 196-147) This invention relates to a clay contactingprocess for treating lubricating oil base stocks and is directlyconcerned with improving the neutralization number of unused,non-additive type lubricating oil stocks.

Refining by adsorption has long been employed as a unit process byrefiners of petroleum products. There are available two difierent typesof processes employing adsorption, namely, vapor phase refining andliquid phase treating. Vapor phase treatment generally has applicationin the refining of relatively light petroleum distillates, especiallycracked gasolines, to improve color and odor and reduce the gum content.Heavier petroleum products such as lubricating oil stocks, however, aregenerally treated in the liquid phase by either passing the oils througha column of granular adsorbents or by mixing the oils in the liquidstate with finely divided solid adsorbents at an elevated temperatureand then filtering the mixture after treatment to recover an improvedlubricating oil stock. The former method is known as percolation and thesecond method is known as contact filtration. Because, in general,contact filtration methods are more economical than percolation typeprocesses, this method is generally used as one processing stage in themanufacture of lubricating oils and it is with this type of process thatthe instant invention is specifically concerned. Contact filtrationprocesses also permit greater flexibility in operating conditions,particularly temperature, as well as in changing feed stocks.

In contact filtration the lubricating oil stock is mixed with a finelydivided adsorbent. This mixture is then heated to an elevatedtemperature. In plant operations the commingling of the adsorbent andthe oil is accomplished by mechanical agitation in a contacting vesselwherein the contacting is carried out at a temperature between about 220to 650 F. Where the heavier stocks are treated, the higher temperaturesof this temperature range are employed. However, various modificationsin the general method of procedure may be employed.

Clay is generally used as the adsorbent in refining by.

contact filtration although other types of solid adsorbents such assilica gel, bauxite, magnesol and the like,'may be which consist ofhydrous employed. 'Ihese clays, alumino silicates, are either of mineralorigin and are the use of contact filtration processes to substantiallyreduce the amounts of the weaker inorganic acids present" either aloneor in combination with the stronger mineral acids in mineral lubricatingoils.

As an indication of the amounts of acidic constituentspresent in theoil, a neutralization value is assigned to the oil after subjecting asample of the oil to the scrutiny of a carefully prescribed procedure.In this test, which is given the A. S. T. M. Designation D974-51T and isfully described in the A. S. T. M. Standards on Petroleum Products-4951published by the American Society for Testing Material, the acidicconstituents are neutralized with a caustic alkali, potassium hydroxide.Neutralization value is generally included in specifications for mostmineral lubricating oils for the purposes of detecting trace amounts ofcorrosive acidic substances in the oils and as Y a refinery control toassure uniformity of composition and characteristics among successivebatches of refined mineral oils. Generally a neutralization value of notgreater than 0.1 is specified as a maximum permissible value forlubricating oil stocks.

Accordingly it is the object of this invention to provide a contactfiltration process for treating lubricating oils affects the activity ofthese adsorbents and that too little I or too much moisture also has aninimical etfect on the efficiency of the clay. Therefore the prior arthas found that in order to treat lubricating oils or other heavypetroleum products, such as vasolines and Waxes, to decolorize andclarify them, it is necessary that the solid adsorbents employed ascontacting agents be treated to remove a substantial portion of thewater adsorbed in the clay. Therefore it has been the practice inpreparing clays for use to dry themto a controlled moisture content. Itis pointed out in the prior art that the tolerable water content ofclays may vary between 5 and 20 percent i A by weight of moisture. Ithas been found, however, that when commercially available clays having awater content between these ranges are employed to reduce the neuusedeither as found in nature in their natural state or after treatment withacid to enhance their adsorptive properties or may be preparedsynthetically. Many of these clays are sold under trade names such asFiltrol, Attapulgus, etc. Although contact filtration processes havebeen used in general to clarify and decolorize lubricating oils, theyare not successfully employed in all instances to neutralize lubricatingoils that have been acid treated, solvent extracted or simply distilled.The adsorbents will readily remove the stronger acidic substances suchas sulfuric acid and other mineral acids from the oils. However, it iswell known that even though organic acids can be removed fromlubricating oils, the use of contact filtration is not resorted to inthese instances because this class of oxygenated compounds can not beremoved economically. A manipulative technique, however, has beendiscovered which will permit tralization number of a lubricating oil,the clay adsorbent is inetfectual'in this application. In order tosuccessfully employ a contact filtration process to neutralizelubricating oils containing organic acid constituents, it is esseni';tial to the instant invention that the contacting process be carried outwith a solid adsorbent which is substantially free from physically boundwater. This water is adsorbed water which is defined as the physicallycom- :bined or adsorbed moisture which may be, removed from the clay bycalcining the adsorbent at temperatures below 400 to 500 F; or at thecontacting temperature employed in effecting a reduction'in theneutralization value.

To demonstrate the effect of adsorbed water on acid removal in contactfiltration, several experiments were conducted wi-th adsorbentslhaving avariety of adsorbed water contents, the variations in moisture controlbeing pro duced by employing several difierent processing techniques.High gas stripping rates, contacting under vacuum, or a combination ofgas stripping and vacuum which removed the adsorbed Water quicklyvvereemployed and as a further alternative, predried clay was employed toeffect a maximum removal of adsorbed water. The equilibrium moisturecontent attained-by usi-ngsteam stripping Patented June 11, 1957 duringthe co ntactin g step wasiused to producean intermediate moisturecontent. Anintermediate moisture content was also obtained by not usingany external stripping under l atmospheric pressure. in air-free.atmosphere.

High moisture content was provided by carrying out the claycontacting inasealedbomb or in a-conventional contacting apparatus which was equippedto reflux the,efflue pr u d. ur nse n c in perat on.- In

th r, he epr ce ures stanti l ll t: he mc s.

ture -was re tained therein, This. experimental work; was carried outwith conventional laboratory equipment. The on act n pp u ns dzq a' sk ted. t

e n met um ch i a rr cntdsas nlet whey;

e 0 i l l ters b antiall sui -e; ub ieating oil stoclc and a; prescribedarnount of the .clay adsorbent were admi'xed-inthe flash to form anoil-adsorbent-slurry. The mixturewas heatedto 400: F. for neutral stocksor; 510 F. for bright stocks andconstantly it t d duflne the e r e. fhefi e tmentw sh Was completed in l0 to 35 minutes. After treating, themixture was allowedto cool slightly to about.5 0- F. below thecontacting temperature and was then filtered to recover a finished oil.Theineutralization value of thisoil, aswell as the neutralization valueof=all finished samples, was obtained by means of the. aforementionedprocedure established by the American Society of Testing Materials. Whennitrogen, carbondioxide or methane were employed as a representativeexample of an inert, desiccated, gaseous stripping medium during thecontacting, the flow rates were measured by suitable metering means. Inthecases where the moisture content of the oil-adsorbent mixtures wasmeasured, the efliuent gases from the contact flask were passed througha moisture trap maintained at a low temperature by means of Dry Ice. Inthis trap the moisture was cooled in a graduated receiver. To avoid thedeleterious effects of oxidation during the heating of the adsorbent-oilslurry, the preheating was carried out under an inert gaseous blanket toinsure that air was not in contact with the heated mixture. In the caseswhere subatmospheric pressures were used, a vacuum was pulled throughthe vent line with the gas inlet tube closed. When both subatmosphericpressures and gas stripping were employed, the gas inlet tube was openedto a supply of the. gas employed. The bomb. experiments which wereemployed to insure complete water. retention during the contacting werecarried outby introducing 100 milliliters oi lubrieatingoil stock alongwith the prescribed amount of lay into a glasslined bomb whichpreviously had bee purgedwith nitrogen. The adsorbent oilwas heated to500 F. and held at this temperature for 30 During this time the bomb wasconstantly shaken to insure contacting of the oil and adsorbent. Aftercooling, the oil slurry was filtered and th e finished oil recovered.Several types of naturally occurring clay were employed in theexperiments, e. g., an acid-treated clay. which had a 16.6% moisturecontent and. an. untreated clay which had a 14.3% moisture content, themoisture content being determined by heating the samples for 30 minutesin a muffle furnaceat 1800 F. This moisture content includes both thestructural water and adsorbed water. Lathe experiments in which themaximum acid value was attained, the moisture content of the clayadsorbent was reduced to the point that substantially the only waterremaining in the clay was structural water. This removal of the adsorbedwater was brought about by oneof several techniques, viz:

(1) Stripping ofthe oil-adsorbent.mixture. duringthe.

(2) Carrying out the contacting of the adsorbent-oil :slurry atsubatmospheric pressures sufiiciently low to effectthis end,

(3) Combining the techniques in 1- and 2 above,

(4) Pretreating the clay adsorbent at an elevatedtemperature to removethe adsorbed water prior tousing the clay as a contacting agent, or

(5) Carrying out the contacting of the adsorbent-oil slurry in thepresence of steam stripping andthereafter stripping the resultant slurryprior to filtering with an inert, desiccated gaseous medium such asnitrogen, natural gas, etc.

As a precautionary measure when rcsortiugto thepretreating techniquewherein the clay is treated at an elevated temperature prior to use toremove the adsorbed moisture, in order to prevent a depreciation ineificiency .of the acid treated types of clay, these substances shouldbe vacuum-dried at about 25 0 F. to remove all of the adsorbed waterfrom the clay. If these claysare heated at higher temperatures of about500 F., the eff ciency ofthe clay might be reduced. This difierencemight be explained by the fact that acid-treated clays might have tracesof the treating acid remaining on theclay to cause a deleteriousefiectin treating efficiency. however is only a surmisal and is not to beconstrued'as alimiting factor of the instanti'nvention. The results-ofthe various experiments inwhi ch an acid-treated-clay was used as the.

adsorbent are reported in Table I,

TABLEI Contacting devmxed bright stock with acid-treated natural clay'StrlppingConditlons. MotstureLoss, Percent. Clay. Contact:v of Orig.Clay N eutral- Run Rate, Time, ization Remarks No. #lbbl. Rate, Min.Value 1 Gas Liter, Pro-drying During Batch of Clay. Contacting 0.10vUntreated oil. 20 Nitrogen 6. 0 30 0 10. 5 0. 03 20 do- 4.2 10 0 11.60.03 20 do 6 0 30 10.5 1 0.03 011: pre-dried-under vacuum to 20 30 0 12.8 0.02 Vacuum contactingat 15 mm. pressure. 20 1. 5 30 10. 5 1 0. 07Clay oven-dried at 600? F. 20 7. 5 30 0 11. 6 0. 02 Steam stripping ofpreviously nitrogen 20 5.1 30 0 0.02 stripped-mixture. I

20- 2.0 10 0 9.9 0.05 20 1.1 10 0 9.9 0.06 20 0.6 10 '0 8.1 0.06 20 0.3.10 0 7.6 0.09 20. 5 30 '0 *7. 5 0.09 Estimated by difference; does notin- Nitrogen 6.0 30 0 2. 5 0,03 elude. moisturaadded' as strippingsteam-N, stripping oi preylously steam stripped mixture. l 18 20 do 230- 7 5 1 0,07 Vacuum. dried lay. Moisture largely V retained byrefluxing. I 14..-.-. 20 do 1.5, 30 0- 0.09 Moisture retained'byrefiuxlng. 15"..- 20' ..'..d'o'... 6:0 30 12.1 0 001- Vacuum dried clay(clayv pro-dried,

' under vacuum 120190 F.) heated'for' 1 hour at BOO 'E. under nitrogen.Ct. r -N TABLE II Contacting dewaxed bright stock with natural clayStripping Conditions Moisture Loss Percent Clay Contact of Orig. ClayNeutral- Run Rate, Time, ization Remarks No. #lbbl Rate, Value GasLiter/ During During Batch Pre-drying Contacting 10 10 *8. 7 2 0.08*Vacuum dried to 250 F.

10 10 9.4 1 0.09 Oven-dried at 500 F.

10 30 0 0.09 Steam stripping otprevlously nitrogenstripped mixture.

10 Nitrogen 0.5 30 5.5 2 0.10 r

10 Steam 30 0 5.8 0.13 Estimated by difierence; does not in- Nitrogem.6.0 30 0 4.0 0.07 elude moisture added as stripping steam-N2 strippingof previously steam-stripped mixture.

10 --do 1. 5 30 0 low 0.12 Moisture largely retained by refluxing.

10 do 0 30 0 0 0. 16 Treated in sealed bomb after nitrogen 10 .do.' 0 30*9.4 0 0. (i ve -di ied at 500 F. Treated in sealed bomb after nitrogenpurging.

Table II contains a tabular summary of a similar set of in acid valuebecame progressively less. For example, experiments in which a naturallyoccurring clay was used where the moisture remaining'in theadsorbent-oil slurry as the adsorbent. It will be noted from thisexperimental was equal to about 40 percent by weight of the adsorbeddata that in the contact filtration treatment of lubricating wateroriginally present in the adsorbent, the acid values oil stocks the mosteiiective acid removal was brought of the finished oils were 0.06 to0.07 higher than those about only when the adsorbent-oil slurry had beendehy obtained by treating the oil under conditions in which drated toremove substantially all of the adsorbed moissubstantially all of theadsorbed water had been removed ture which normally would be retained onthe adsorbent from the adsorbent. In those experiments in which variatthe temperature of contacting. In the instant study this ous. otherintermediate adsorbed water contents were proamounted to about 12percent by weight of the acidvided, the effectiveness of the treatingprocess for reductreated clay which had 16.6 percent by weight totalmoising-ihe neutralization value was correspondingly limited. ture and10 percent of the natural clay which had 14.3 To further illustrate theinstant invention additional percent total moisture. It is obvious thatin the event experiments, the results of Which are tabularly sumthatadsorbents having a higher moisture content were marlled In Tables V andConducted} t0 employed, larger amounts f adsorbed Water would hdemonstrate the critical feature of the instant invention, to be removedto provide a maximum reduction in acid ViZ., conducting the contactingfor a time sufficient to value. It will be noted that equivalent resultswere ob- 40 remove m the 3.01m 'ads'otbent all of the adsorbfd tainedwhether the substantially complete removal of adg. f f f q i hAithoughthe pnor sorbed water was obtained by either stripping with sufli- E 15cose.s 51m ar mampu atlve tec i i t amount of a .nert de iccated aseo smedium mg contacting processes to eifect decolorization of lubris n S ueating oil stocks, the prior art workers have failed to such asnitrogen, carrying out the contacting at subatm'ospheric pressures,sufliciently low to effect the complete removal, or employing a clayadsorbent which had previously been heated to remove substantially allof the adsorbed water. It is also seen that, by permitting morerecognize the essential feature of removing substantially all theadsorbed water from the adsorbent where reduc tion in neutralizationvalue is an important objective in the finishing of lubricating oilstocks.

Table III contains the results of experiments using an moisture toremain in the contact mixture, the reduction acid-treated clay in thecontacting of a dewaxed bright 7 TABLE III Contacting dewaxedbrightstock with acid-treated clay-Variation in contact time Charge OilTreated 011 Clay Percent Contact Contact Vacuum Run No. Rate, MoistureTemp., Time, in Hg #lbbl. in Clay F. Min. Neut. Color Neut. Color ValueValue TABLE IV Contacting dewaxed bright stock with acid-treatedclay-Variation in stripping medium Stripping Medium Charge oil Treatedoil Clay Percent Contact Contact Pressur Run No. Rate, Moisture Temp.,Time, Atm.

#lbbl. in Clay F. Min. Type Rate N eut. Color Neut. Color Value Value 1523.3 510- 35 Steam--. 1 0.19 4+ (dll.) 0.10 +5 15 23.3 512 35 COzcu.ftJbbl- 1 O. 19 4+ (dil.) 0.03 +5 15 23.3 513 35 None 1 0. 19 4+ (dil.)0.10 5

stock in which the time of contact was varied. It was found that thetime requiredfor essentially maximumcolor improvement was insufiicientfor maximum reduction in neutralization value. Most eflicient use ofclay for decolorization purposes does not require the removal ofadsorbed moisture. This is further illustrated in Table IV where the useof steam in the contacting operation does not allow the removal 'of'suflicient moisture to give maximum reduction in neutralization valuebut does allow maximum improvement in color of the finished oil.

Table V presents data on the contacting of dewaxed bright stock with anacid-treated clay in which methane stripping, vacuum and combinationsthereof were employed. At very low gas stripping rates or atintermediate vacuum, maximum reduction inneutralization value was notachieved while good decolorization was. In the light of experiments inwhich the moistureremoval from the contact mixtureswas measured, this isinterpreted as the result of failure to remove enough of the adsorbedmoisture. Increased gas stripping rates, in-

It more be concluded that it has been discovered that moisturercmovalfromthe adsorbent is directly correlated to reduction in neutralizationvalue. In applying this discovery to, the conventional contactfiltration process it is seen that .it is possibleto' substantiallyreduce the neutralization value, improve the color and reduce theemulsification tendencyby a methodwhich does not increase the 'ashcontent of the oils of a lubricating oil stock regarda less of whetherthe neutralization value is caused by the a 'cated, non-oxidizinggaseous medium such as nitrogen creased vacuum or combinations thereofwere found to produce greater reduction in neutralization value of thefinished oil, without further improvement in col-or, which demonstratesthe critical features; of the instant invention.

Table VI illustrates the improvement in neutralization value reductionto be expected when employing moisture' removing conditions tothecontacting of a distilled dewaxed lubricating stock.

gave approximately the same color improvement indicating that the colorremoval properties of the clay are independent of the moisture contentof these adsorbents. Furthermore the time element involved in thecontacting operation is also critical. It has beendemons'trated that thetime of oil-clay contact necessary for. substantially completeclarification and decolorization of the lubricat ing oil is notsufiicient to eifectmaximum neutralization v value reduction of saidoil. A finite time dependent upon the amount of moisture, method ofremoval, type of equipment employed, etc., is required to remove themoisture and h'e'nce efiect maximum neutralization number reduction;this'ti'me bein'g independent of the time required for de'colorization.

What is claimed is: V

I. In a process forreducing-the'neutralization value of TABLE VContacting dewaxed bright stock with acid-treated clay -Variationinstrippiitg rate Stripping Medium Charge Oil Treated Oil Steam Run 01sPercent Contact Contact a Emul- N 0. Rate, Moisture Temp., Time,Pressure slon #lbbl. in Clay F. Min. Type Rate, cu. Neut Color .NeutColor umftJbbi. Value Value her" 10 23.3 610 Methane-- 0. 16 7+ 0.09 96+10 23. 3 512 35 d 0. 15 7+ 0. 08 96+ 350 10 23. 3 515 d 0. 15 7+ 0. 05456+ 385 10 23. 3 510 0. 15 7+ O. 14 4}+ 10 23. 3 510 0. 15 7+ 0. 10 4$+405 10 23.3 510 35 do 24' vac 0.15 7+ 0.05 4%+ 10 23. 3 615 35 Methane;10 V" 0. 15 7+ 0. 05 10 23.3 615 35 ..d0 18 15" vac 0.15 7+ 0.05 l 5+367 s. E. No. 900. V ABTM Designation: D157-51.

TABLE VI Contacting dewax'ed neutrulivith natural clay- Variation instripping medium stripping Medium Charge on Treated 011 Clay PercentContact Contact Run No. Rate, Moisture Temp, Time, Pressure #lbbl. inClay F. Min. Type Rate Neut. Color Neut. Color Value Value 15. 4 410 35(:11 fl; lbbL. 0 15 +2 0.04 156+ 7 15. 4 405 35 tm 0;15 +2 0. 13 D-ll5.4 400 35 0. 15 +2 0. 04 1%+ In practicing this invention'theconventional type of contacting equipment can be employed whenmodified'to permit the use of inert, desiccated gaseous stripping mediumor subatmospheric pressure in the contacting vessel. The contacting maybe carried out at temperatures between about 350 to 550 F. As inconventional 'decoloriz'ing by contact filtration, the same economicalclay dosages may be employed; viz.', 3 pounds to 15' pounds of acidtreated or natural clay'per barrel "of oil. However in m instan t ma air dt a s a ou of clay be used. The time of contacting will depend uponthev quantity of oil being treated and the efiicie'n'cy of moistureremovalbut generally a 35 minute treat-is-'sufficient where commerciallyavailable clays are used in the conventional contacting process.

a lubricating oil the step which comprises intimately contacti'ngat atemperature of about 35055 0 F. an organic acid-containing lubricatingoil with 3-15 pounds per barrel of oil of a hydrous alumino-silicateadsorbent from which substantially all of the bound water is removedwithout deleteriously' effecting the structural water content cf saidadsorbent for a time sufficieut to produce a substantial improvement inthe neutralization value reduction-of said oil, said contacting beingconducted in the absence of air and steam, and maintained in ananhydrous condition by stripping during said contacting any moisturewhich is produced during said contacting.

'2. In aproce'ss for reducing the neutralization value of an-organicacid-containing lubricating oil stock which comprises admixing 3-l5pounds/barrel of oil of a hyaim. gm aw drous alumino-silicate adsorbentto form an adsorbentoil slurry, agitating said slurry in a contact zoneat a temperature of about 350 550 F. in the absence of air and steam fora time in excess of the time required to produce a maximum colorimprovement in said oil and sufficient to effect a further and maximumreduction in the neutralization value achieved in the time required toproduce maximum color improvement, stripping from said zone during saidagitating any moisture Which is produced during said agitation wherebysaid zone is maintained substantially free of accumulated Water, andfiltering the treated oil and clay, said adsorbent during said agitatingbeing substantially free of adsorbed Water without deleteriouslyaffecting the structural water content of said adsorbent.

3. A process in accordance with claim 2 in which said agitating iscarried out in the presence of, and said stripping accomplished by, aninert gaseous stripping medium which is introduced at a rate sufficientto purge said zone of air, free said adsorbent from adsorbed water underthe contacting conditions in said zone, and maintain said zonesubstantially free from accumulated Water during said agitating.

4. A process in accordance with claim 3 in which said adsorbent has beenpretreated prior to said admixing to remove substantially all of theadsorbed water therefrom without deleteriously affecting the structuralWater content of said adsorbent.

5. A process in accordance with claim 2 in which said stripping isaccomplished by carrying out said agitating at a subatmospheric pressuresufiiciently low to remove substantially all of the air from said zone,free said adsorbent from adsorbed Water, and maintain said zonesubstantially free from accumulated moisture.

6. A process in accordance with claim 5 in which said adsorbent has beenpretreated prior to said admixing to remove substantially all of theadsorbed Water therefrom without deleteriously affecting the structuralwater content of said adsorbent.

7. A method for reducing the neutralization value of a lubricating oilstock which has been subjected to intimate contact with a hydrousalumino-silicate adsorbent to remove therefrom a substantial quantity ofnaturally occurring color bodies which comprises admixing with said oil3-15 pounds per barrel of oil of a hydrous aluminosilicate adsorbent toform an adsorbent-oil slurry, agitating said slurry in a contacting zoneat a temperature of about 350-550 F. in the absence of air and steam fora time suilicient to effect a maximum reduction in neutralization valuesurpassing the reduction in neutralization value achieved in thetreatment of said oil to remove therefrom a substantial quantity ofnaturally occurring color bodies, stripping from said zone during saidagitating any moisture which is produced during said agitating wherebysaid zone is maintained substantially free of ac cumulated moisture, andfiltering the treated slurry to separate the treated oil and clay, saidadsorbent during the agitating being substantially free of adsorbedWater without deleteriously affecting the structural water content ofsaid adsorbent.

References Cited in the file of this patent UNITED STATES PATENTS2,045,160 Moorman et al. June 23, 1946 2,563,369 Reiley et al. Aug. 7,1951 2,572,433 Bergstrom et al. Oct. 23, 1951 2,585,491 Olsen Feb. 12,1952 2,621,149 Scott et a1 Dec. 9, 1952 2,651,602 Davis et a1. Sept. 8,1953 2,679,471 Ayers et al May 25, 1954 OTHER REFERENCES Mantell:Absorption, First Edition, McGraw-Hill Book Co., New York, N. Y., 1945,page 49.

Sachanen: The Chemical Constituents of Petroleum, Reinhold PublishingCorp., 330 W. 42nd Street, N. Y. (1945), page 320.

1. IN A PROCESS FOR REDUCING THE NEUTRALIZATION VALUE OF A LUBRICATINGOIL THE STEP WHICH COMPRISES INTIMATELY CONTACTING AT A TEMPERATURE OFABOUT 350*-550*F. AN ORGANIC ACID-CONTAINING LUBRICATING OIL WITH 3-15POUNDS PER BARREL OF OIL OF A HYDROUS ALUMINO-SILICATE ADSORBENT FROMWHICH SUBSTANTIALLY ALL OF THE BOUND WATER IS REMOVED WITHOUTDELETERIOUSLY EFFECTING THE STRUCTURAL WATER CONTENT OF SAID ADSORBENTFOR A TIME SUFFICIENT TO PRODUCE A SUBSTANTIAL IMPROVEMENT IN THENEUTRALIZATION VALUE REDUCTION OF SAID OIL, CONTACTING BEING CONDUCTEDIN THE ABSENCE OF AIR AND STEAM, AND MAINTAINED IN AN ANHYDROUSCONDITION BY STRIPPING DURING SAID CONTACTING ANY MOISTURE WHICH ISPRODUCED DURING SAID CONTACTING.